Effect of Ti particles on the microstructures and mechanical properties of Ti particle reinforced Mg-9Gd-2Y–1Zn-0.5Zr composites

The Ti particle (1, 3, 5 wt.%) reinforced VW92 (Mg-9Gd-2Y-1Zn-0.5Zr) composites were successfully fabricated by semi-solid stirring assisted by ultrasonic treatment and subsequent hot extrusion. The microstructural characterizations revealed that the Ti particles significantly promoted the formation of RE-rich phase in the matrix. The competition between RE-rich and LPSO phase on RE element made the low content of lamellar LPSO phase in the 3Ti/VW92 composite. The (Gd, Y)H 2 phase was formed on the surface of Ti particles, forming a coherent interface with Ti particles. The grain size showed a downward trend from 8.60 μm to 3.04 μm with the addition of 5% Ti particles. The dynamic recrystallization (DRX) was promoted by Ti particles while inhibited by RE-rich and lamellar LPSO phases in the Ti reinforced VW92 composites. The tensile results showed that the 5Ti/VW92 composite possessed the optimum comprehensive mechanical properties with yield strength, ultimate tensile strength and elongation of 255 MPa. 378 MPa and 12.08%, respectively. The improvement of mechanical property was ascribed from the effective load transfer from Mg matrix side to the Ti particle, precipitation strengthening from RE-rich phase, dislocation strengthening and grain refinement strengthening caused by Ti particles. The deformability of Ti particles and the good interfacial bonding were beneficial for maintaining the good ductility of Ti reinforced VW92 composites.